One-hour plasma glucose pinpoints older men at risk of T2DM

Elevated 1-hour plasma glucose (PG) levels convey an increased risk of developing type 2 diabetes mellitus (T2DM) in older men, according to a study.

“This emphasizes the benefit of identifying abnormalities in glucose metabolism early to allow timely therapeutic intervention,” the investigators said.

They evaluated the predictive capabilities of fasting (F)PG, 1 h-PG, and 2 h-PG values obtained during oral glucose tolerance test (OGTT) in 928 diabetes-free older men (median age, 73 years; mean waist circumference, 89.4 cm; mean body mass index of 25.2 kg/m²) who were followed for more than 20 years.

At baseline, 533 men (57 percent) had normal glucose tolerance (NGT), 57 (6 percent) had isolated impaired fasting glucose (IFG), 273 (29 percent) had isolated impaired glucose tolerance (IGT), and 65 (7 percent) had both IFG and IGT. Overall, they had mean triglyceride, total cholesterol, and high-density lipoprotein (HDL) levels of 1.8, 5.3, and 1.2 mmol/L, respectively. 

More than half of the population (62 percent) developed T2DM over the follow-up. In a Cox proportional hazards regression model, 1 h-PG and 2 h-PG values emerged as significant predictors of T2DM (hazard ratio [HR], 1.269, 95 percent confidence interval [CI], 1.214–1.327; p<0.001 and HR, 1.269, 95 percent CI, 1.179–1.366; p<0.001, respectively). These associations persisted despite adjusting for various traditional risk factors. [Diabetes Res Clin Pract 2021;doi:10.1016/j.diabres.2021.108683]

However, 1-h PG showed a much greater predictive ability than 2-h PG in models incorporating various traditional risk factors (C-statistics, 0.794, 95 percent CI, 0.765–0.823 vs 0.747, 95 percent CI, 0.716–0.779).

Likewise, the area under the ROC curves were better for 1-h PG than 2-h PG (0.766 vs 0.719).

Not miss a diagnosis

The findings suggest that “1h-PG values can identify potential diabetic risk in individuals who would otherwise be neglected, [given that] clinicians usually focus on individuals with high FPG or 2h-PG,” according to the investigators.

“Such conventional clinical practices may miss some patients at potential risk with FPG and 2h-PG values within the normal or borderline ranges. Among elderly men without known diabetes, 1h-PG provides better prognostic yield than both FPG and 2h-PG in predicting long-term diabetes, both isolated and in addition to a clinical prediction model,” they added.

Insulin resistance and β cell dysfunction are two major risk factors for hyperglycaemia and T2DM. Normal glucose homeostasis to the onset of T2DM is said to occur in three different phases, with the entire process taking more than 10 years. Notably, some people develop T2DM with normal FPG and 2h-PG at baseline. [Diabetes Care 2014;37:S81-S90; Lancet 2009;373:2215-2221; J Clin Endocrinol Metab 2005;90:493-500]

“Therefore, it can be concluded that individuals with NGT and high 1h-PG values have reduced glucose sensitivity of β cells but maintain NGT due to residual β cell mass and retain second-phase insulin secretion,” the investigators explained. “Higher 1h-PG may reflect impaired insulin secretion in the first phase, and elevated 2h-PG in the second or late phase.”

As such, elevated 1h-PG levels may provide an opportunity for early identification of large numbers of people at risk, they continued.

Upon detection of elevated 1h-PG levels, clinicians should recommend lifestyle interventions to maintain β cell function or reverse its decline and prevent further progression to prediabetes and diabetes, the investigators said. [Endocrine 2013;44:66-69]